This invention relates to intraocular lenses (IOLs) More particularly, the invention relates to IOLs placed in the anterior chambers of eyes which provide at least one of the following benefits: a reduction in the incidence of one or more complications in the eye caused by prior anterior chamber IOLs, effective foldability for safe and controlled insertion in the eye through a small incision, reduced IOL retention forces and a reduction in the tendency of the optics of the IOLs to vault due to a desirable compressive bias of the IOL when fit within the eye.
Intraocular lenses (IOLs) are commonly used to modify or enhance vision. IOLs can be placed at various positions or locations within the eye. For example, IOLs can be placed in the anterior chamber (AC) of the eye, that is, the region of the eye posterior of the cornea and anterior of the iris.
IOLs may generally be classed by material. Hard or rigid IOLs are distinguished from soft IOLs that may be folded to facilitate implantation through a small incision in the cornea (and capsular bag for posterior lenses).
Although there are substantial advantages to placing the IOL in the anterior chamber of the eye, various complications have been reported as a result of the presence of IOLs in such anterior chambers. For example, anterior chamber IOLs have been reported to cause detrimental endothelial cell loss in the eye; pupil retraction or ovalling, which can be both cosmetically and functionally detrimental; pupillary block, which can cause glaucoma; and decentration or offsetting displacement of the IOL away from a preferred optical axis. Such complications are particularly troublesome when the anterior chamber IOL is structured to be fixated against the iridio/corneal angle, a very delicate region of the eye. It would be advantageous to provide anterior chamber IOLs which result in reduced incidences of one or more of these complications.
IOLs advantageously have been foldable for insertion through small incisions in eyes, particularly for insertion in the capsular bags in the posterior chambers of the eyes. Because of space constraints in and the delicacy of the anterior chamber, IOLs for insertion in the anterior chamber are not generally foldable. For example, IOLs have a tendency to move in a relatively uncontrolled manner upon unfolding in the eye. Such uncontrolled movement of an IOL in the anterior chamber can detrimentally affect the iris and/or the cornea. For example, the IOL touching the cornea can result in harmful endothelial cell loss.
When implanted, both soft and rigid anterior chamber IOLs exert retention forces on their outer ends; that is, the IOL is typically slightly oversized relative to the peripheral anterior chamber structure. A slight amount of such retention forces is desirable so that the lens is held in place or centered, otherwise a loose fit might cause vision and other problems. Indeed, some earlier rigid IOLs were unsatisfactory because of sizing difficulties, in that the size of the IOL relative to the surrounding tissue was critical. On the other hand, both xe2x80x9crigidxe2x80x9d and xe2x80x9csoftxe2x80x9d IOLs may be provided with some flexibility in the plane of the IOL to mitigate against such sizing concerns. The term xe2x80x9cplanexe2x80x9d or xe2x80x9csurfacexe2x80x9d of the IOL will be used to denote the surface (and extension thereof) of the optic portion of the IOL, though it will be understood that such a xe2x80x9cplanexe2x80x9d may actually be a partial sphere or other curved surface.
As stated, anterior chamber IOLs may be oversized and flexible in the plane of the IOL such that they are placed in compression when implanted. However, a balance must be observed between sufficient compression for a good fit and unwanted endothelial cell loss and pupil ovalling from excessive compression. In addition, the design of the footplates must be such that over time, pupil block and glaucoma does not result. Finally, the problems of corneal touch and further endothelial cell loss may arise in some current IOLs, whether formed of soft or rigid materials, which may deflect along the optical axis even with only a small magnitude of compressive fit. As a result, IOL manufacturers must provide a range of sizes to fit the IOL to a particular patient""s eye and reduce, or even substantially minimize, retention forces and the potential for axial deflection.
U.S. Pat. No. 5,928,282 discloses an intraocular lens having haptics that are flexible to minimize translational motion of the optic along the optical axis. The patent discloses a central portion (38) extending between a foot plate on the outer end of the haptic and the IOL optic that has a thickness dimension (parallel to the optical axis) equal to or greater than a width dimension. A transition portion (44) extends from the central portion to the foot plate and has a gradually decreasing thickness and increasing width, with the foot plate being relatively flat. In this design, the central portion is flexible to mitigate against the perceived problem of inward compression of the surrounding eye without undue axial movement, or doming, of the optic. Unfortunately, the central portions extend to within proximity of the optic, and their flexibility thus creates the potential for unwanted optic movement. That is, the dynamic system of the IOL consists of the optic supported within a number of relatively flexible haptics.
It would be advantageous to provide soft anterior chamber IOLs which provide one or more of the following: reduced incidences of one or more known complications caused by prior anterior chamber IOLs, are effectively and safely foldable for insertion in the eye, safely and effectively fit a range of sizes of eyes, provide reduced retention forces, minimize translational movement of the optic of the IOL along the optical axis from the compressive fit in the eye, and which otherwise stabilize the optic from unwanted movement.
New IOLs for implantation in eyes, in particular in anterior chambers of the eyes, have been discovered. The present IOLs are sized and structured to reduce the incidence of one or more known complications in the eye caused by prior anterior chamber IOLs. The present IOLs are designed to be effectively fixated against the iridio/corneal angle of the anterior chamber while being substantially compatible with this delicate region of the eye. Reduced endothelial cell loss and/or reduced pupil ovalling and/or reduced pupilliary block, for example, relative to prior anterior chamber IOLs, are obtained in accordance with the present invention.
The present IOLs are foldable for insertion through a small incision in the eye. In particular, the IOLs of the present invention are designed and structured to be folded and inserted, for example, using a forceps or a conventional system used to fold and insert folded IOLs in eyes, effectively and safely. The present IOLs preferably are structured to unfold in the eye in a substantially controlled manner which advantageously reduces the risk of the unfolding IOL causing damage to the eye.
In the eye, the IOL is effectively fixated against the iridio/corneal angle. In this position, the IOL is advantageously stabilized, exerts reduced retention forces, and the optic of the IOL has a substantially reduced tendency to vault anteriorly.
In one embodiment, the present invention provides a foldable intraocular lens (IOL) for implantation in the anterior chamber of an eye. The IOL includes an optic centered on an optical axis, the IOL defining a planar or domed surface that is substantially perpendicular with respect to the optical axis at least at its intersection with the optical axis. At least one fixation member having a proximal end is secured to the optic. An intermediate region extends generally radially outwardly from the proximal end, and a distal region secures to an outer portion of the intermediate region. The distal region includes at least one leg portion extending away from the outer portion of the intermediate region generally perpendicularly with respect to a radial line (relative to the optical axis) through the intermediate region. The leg portion is able to flex in a direction parallel to the planar or domed surface of the IOL while the intermediate region is substantially unable to flex in a direction parallel to the planar or domed surface of the IOL.
In a preferred embodiment, the IOL includes only two of the fixation members. The distal region may have two leg portions extending away from each other in substantially opposite directions, and the two leg portions may extend away from each other a distance equal to or less than a diameter of the optic to facilitate folding of the IOL. Desirably, the leg portions each have an enlarged footplate on an outer end extending radially outwardly therefrom. When implanted, the leg portions are each structured to flex in response to a radially-inwardly directed biasing force being applied to the respective footplate secured thereto. More generally, the leg portion is structured to flex substantially without moving the optic parallel to the optical axis.
In accordance with one aspect of the invention, the intermediate region has a circumferential width about the optical axis which is substantially smaller adjacent the outer portion than it is adjacent the proximal end. Preferably, the intermediate region has a circumferential width that is at least twice as large as its axial thickness at all points. The IOL may be a single piece lens, or the optic and the fixation members may comprise one or more polymeric materials. In a preferred embodiment, the optic comprises a resiliently deformable polymeric material. In one form, the fixation member exhibits an angular transition so as to be stepped from the plane of the IOL.
In accordance with another aspect of the invention, a foldable intraocular lens (IOL) having reduced optic vaulting for implantation in the anterior chamber of an eye is provided. The IOL includes an optic centered on an optical axis, the IOL defining a planar or domed surface that is substantially perpendicular with respect to the optical axis at least at its intersection with the optical axis. At least one fixation member having a proximal end is secured to the optic. An intermediate region extends generally radially outwardly from the proximal end and a distal region secures to an outer portion of the intermediate region. The distal region is able to flex in a direction parallel to the planar or domed surface of the IOL. The intermediate region has a circumferential width about the optical axis which is substantially smaller adjacent the outer portion than it is adjacent the proximal end. Preferably, the intermediate region has a circumferential width that is at least twice as large as its axial thickness at all points. More preferably, the intermediate region has a diverging circumferential width from the outer portion to the proximal end thereof.
Any and all of the features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.